1. Field of the Invention
The present invention relates to a trigger query obtaining apparatus and the like for obtaining trigger queries.
2. Description of the Related Art
In recent years, search engines have been used on the Internet on a daily basis. When a query having one or more keywords to be used for a search is input, a search engine outputs search results for the query. The input query may be sometimes used for a purpose other than searching. One example is keyword-targeted advertising in which an advertisement corresponding to the input query is distributed (for example, see Japanese Unexamined Patent Application Publication No. 2013-84264). In keyword-targeted advertising, when a query associated with a preset advertising keyword is entered, an advertisement corresponding to the advertising keyword is distributed.
Keyword-targeted advertising has a problem in that an advertisement will not be so often displayed if the number of advertising keywords is small. In keyword-targeted advertising, for example, if “cabbage” and “lettuce” are set in advance as advertising keywords for a vegetable market, an advertisement will not be displayed in response to a non-advertising keyword such as “tomato”. In this manner, it is more desirable to have more keywords corresponding to information to be presented. However, a set of keywords that cover the information is difficult to obtain by human effort.
In general, it is difficult to obtain a set of keywords that cover a certain category by human effort.